DCMPMS Seminars

Twisted graphene heterostructures for next-generation broadband photodetectors

by Mr. Hitesh Agarwal (Institution ICFO, Barcelona)

Monday, December 20, 2021 from to (Asia/Kolkata)
at TIFR ( D-405 )
In the past few decades, there has been a tremendous increase in demand for discrete imaging  and diagnostics techniques in defence, security and even in our day to day life. It is very desirable to check post-packaging products like medicine, food, and industrial equipment unobtrusively. However, traditional X-ray detectors have limited resolution and result in long term side effects. Hence, a lot of efforts are recently being carried out to explore fast and sensitive imaging techniques in the THz to Mid-infrared (MIR) range. The electromagnetic waves in this range have very low energy photons and can pass through almost lossless through everything without any damage. So far, the current market-dominating technology for THz and infrared detection is based on HgCdTe (MCT). Although very sensitive, these detectors have a very narrow operating spectral range. Hence, there is a need for a sensitive detector with the broadband operation.  

In the last few years, graphene-based systems have emerged as promising candidates for optoelectronic applications. They are broadband, fast and CMOS compatible, which makes them an excellent candidates for infrared and THz applications [1, 2]. Further, due to recent advancements in fabrication techniques, twisted graphene heterostructures are quickly emerging as an exceptionally tuneable system for a myriad of optoelectronics applications [3, 4]. In this talk, I will discuss a number of graphene systems including bilayer graphene, twisted double bilayer graphene and hBN aligned bilayer graphene superlattieces. I will discuss how we engineer the bandgap in these systems to generate a strong photoconductive signal in a broad spectral range. I will further comment on the benchmarking of our system with state-of the-art MCT detectors and its industrial relevance. 



[1] Yan, J. et al., Dual-gated bilayer graphene hot-electron bolometer, Nature Nanotech 7,  472–478 (2012). 

[2] Castilla, S. et al., Fast and Sensitive Terahertz Detection Using an Antenna-Integrated  Graphene pn Junction, Nano Lett. 19, 5, 2765-2773 (2019). 

[3] Deng, B. et al., Strong mid-infrared photo response in small-twist-angle bilayer graphene,  Nature Photonics 14, 549-553 (2020). 

[4] Hesp, N.C.H., et al., Nano-imaging photo response in a moiré unit cell of minimally twisted  bilayer Graphene, Nature comm. 12, 1640 (2021).